Conventionally, as illustrated in, for example, PTL 1 below, there is a known disc brake device including pressing means (cam pressing mechanism for a parking brake) for mechanically giving a pressing force via an operation by an occupant in addition to a hydraulic mechanism for giving a pressing force to a piston via a hydraulic pressure.
The conventional device has a single protrusion to be fitted to the front surface of the piston on the back plate of friction pads to prevent the piston from being rotated using the friction pads and an engaging hole into which the protrusion is fitted is provided in the shim plate to prevent the shim plate as well as the piston from being rotated.